<s>
The	O
wavefront	B-Protocol
expansion	I-Protocol
algorithm	I-Protocol
is	O
a	O
specialized	O
potential	B-General_Concept
field	I-General_Concept
path	O
planner	O
with	O
breadth-first	B-Algorithm
search	I-Algorithm
to	O
avoid	O
local	O
minima	O
.	O
</s>
<s>
The	O
nearest	B-Algorithm
neighbors	I-Algorithm
are	O
analyzed	O
first	O
and	O
then	O
the	O
radius	O
of	O
the	O
circle	O
is	O
extended	O
to	O
distant	O
regions	O
.	O
</s>
<s>
Path	B-Algorithm
planning	I-Algorithm
is	O
solved	O
by	O
many	O
different	O
algorithms	O
,	O
which	O
can	O
be	O
categorised	O
as	O
sampling-based	O
and	O
heuristics-based	O
approaches	O
.	O
</s>
<s>
Before	O
path	B-Algorithm
planning	I-Algorithm
,	O
the	O
map	O
is	O
discretized	B-Algorithm
into	O
a	O
grid	O
.	O
</s>
<s>
The	O
potential	B-General_Concept
field	I-General_Concept
path	B-Algorithm
planning	I-Algorithm
algorithm	I-Algorithm
determines	O
the	O
direction	O
of	O
the	O
robot	O
for	O
each	O
cell	O
.	O
</s>
<s>
The	O
question	O
for	O
the	O
potential	B-General_Concept
field	I-General_Concept
algorithm	O
is	O
:	O
which	O
cell	O
is	O
labeled	O
with	O
which	O
direction	O
?	O
</s>
<s>
In	O
the	O
case	O
of	O
path	B-Algorithm
planning	I-Algorithm
,	O
the	O
graph	O
contains	O
the	O
spatial	O
nodes	O
which	O
can	O
be	O
observed	O
by	O
the	O
robot	O
.	O
</s>
<s>
The	O
decision	O
is	O
made	O
on	O
a	O
geometrical	O
level	O
which	O
is	O
equal	O
to	O
breadth-first	B-Algorithm
search	I-Algorithm
.	O
</s>
<s>
That	O
means	O
,	O
it	O
uses	O
metrics	O
like	O
distances	O
from	O
obstacles	O
and	O
gradient	B-Algorithm
search	I-Algorithm
for	O
the	O
path	B-Algorithm
planning	I-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
The	O
algorithm	O
includes	O
a	O
cost	O
function	O
as	O
an	O
additional	O
heuristic	B-Algorithm
for	O
path	B-Algorithm
planning	I-Algorithm
.	O
</s>
<s>
Existing	O
implementations	O
use	O
a	O
queue	B-Application
to	O
store	O
a	O
wave	O
data	O
structure	O
created	O
around	O
the	O
robot	O
.	O
</s>
<s>
A	O
typical	O
implementation	O
in	O
Python	B-Language
can	O
be	O
realized	O
in	O
around	O
200	O
lines	O
of	O
code	O
.	O
</s>
